LSHIY Campaign Exploited OAuth ROPC and IPv6 to Spray Passwords at Scale

A large-scale password-spraying campaign dubbed LSHIY targeted Microsoft Entra ID tenants by abusing OAuth's Resource Owner Password Credentials (ROPC) flow, which bypasses multi-factor authentication prompts entirely. Attackers harvested credentials from public sources and data leaks, then slowly tested one password against many accounts to avoid triggering lockouts. Over a two-week period, more than 81 million login attempts were recorded, resulting in at least 78 compromised accounts. To evade IP-based detection, the threat actors leveraged BYOIP infrastructure and vast IPv6 address ranges linked to entities such as LSHIY LLC, FranTech, and Tor exit nodes. No post-compromise activity was confirmed, suggesting the operation may have been focused on credential validation or resale rather than immediate exploitation.